1. Field of the Invention
The present invention relates to a plastic interlayer having a novel surface structure which is suitable for an adhesive film for a laminated glass and laminated plates such as a solar battery or plastics and glass composites.
2. Description of the Prior Art
An interlayer made of a plastic resin such as polyvinyl butyral, polyacryl resins and polyurethanes has been used as an adhesive film or a reinforcing film for laminating surfaces in a laminated glass and laminated plates such as a solar battery obtained by laminating a silicon wafer photogalvanic sheet between glass plate and a back sheet. For example, in the preparation of the laminated glass, the laminated glass product is prepared by an insertion of an interlayer between glass plates, a preliminary press-bonding process and a final press-bonding process. A nip-roll process, a heat-melt compression or a rubber bag suction can be employed for a pressing and a deairing in the preliminary press-bonding process.
In order to prevent blocking of interlayers, to improve processibility for insertion of an interlayer between glass plates and to improve the deairing effect in the preliminary press-bonding process, a rough surface or a surface having a parallel waved surface is formed on one or both of surfaces thereof, wherein the rough surface forms a random surface having different heights of crests and depths of roots and the parallel waved surface has many parallel grooves. The random surface or the parallel waved surface imparts certain effect for improving the prevention of blocking of interlayers and the processibility for insertion between a pair of glass plates. However, the deairing effect in the preliminary press-bonding is not satisfactorily performed to embed air between the glass plates and the interlayer after the preliminary press-bonding thereby causing serious adverse effect to the durability in bubbling and delamination of the laminated glass after the final press-bonding.
It has been proposed to use the interlayer having a rough random surface in U.S. Pat. No. 4,035,549. The rough random surface has different depths of valleys whereby the deairing property in the preliminary press-bonding is not satisfactory to embed air between the glass plates and the interlayer.
In case of vacuum deairing process, to find optimum process conditions to attain adequate deairing, various tests have been carried out to select a suitable vacuuming rate and a suitable temperature during vacuuming. The testing results show that a conventional interlayer has disadvantages in deairing performance. The conventional interlayer has narrow allowable temperature range. Then, laminated glasses with the conventional interlayer after the final press-bonding show high level of defects caused by residual air resulted by poor deairing during the preliminary press-bonding. Therefore it is not easy to improve productivity of laminating process. In the deairing process by a nip-rolls press or a compression, similar disadvantage has been found. The result is usually inferior to that of the deairing process by the vacuuming.